Make 'Context' immutable.

Move mutable properties back to ServerSession.

Signed-off-by: Bradley Grainger <bgrainger@gmail.com>

src/MySqlConnector/Core/ConnectionPool.cs

@@ -65,7 +65,7 @@ public async ValueTask<ServerSession> GetSessionAsync(MySqlConnection connection
 				}
 				else
 				{
-					if (ConnectionSettings.ConnectionReset || !session.Context.IsInitialDatabase())
+					if (ConnectionSettings.ConnectionReset || session.DatabaseOverride is not null)
 					{
 						if (timeoutMilliseconds != 0)
 							session.SetTimeout(Math.Max(1, timeoutMilliseconds - Utility.GetElapsedMilliseconds(startingTimestamp)));

src/MySqlConnector/Core/Context.cs

@@ -4,26 +4,16 @@ namespace MySqlConnector.Core;
 
 internal sealed class Context
 {
-	public Context(ProtocolCapabilities protocolCapabilities, string? database, int connectionId)
+	public Context(ProtocolCapabilities protocolCapabilities)
 	{
 		SupportsDeprecateEof = (protocolCapabilities & ProtocolCapabilities.DeprecateEof) != 0;
 		SupportsCachedPreparedMetadata = (protocolCapabilities & ProtocolCapabilities.MariaDbCacheMetadata) != 0;
 		SupportsQueryAttributes = (protocolCapabilities & ProtocolCapabilities.QueryAttributes) != 0;
 		SupportsSessionTrack = (protocolCapabilities & ProtocolCapabilities.SessionTrack) != 0;
-		ConnectionId = connectionId;
-		Database = database;
-		m_initialDatabase = database;
 	}
 
 	public bool SupportsDeprecateEof { get; }
 	public bool SupportsQueryAttributes { get; }
 	public bool SupportsSessionTrack { get; }
 	public bool SupportsCachedPreparedMetadata { get; }
-	public string? ClientCharset { get; set; }
-
-	public string? Database { get; set; }
-	private readonly string? m_initialDatabase;
-	public bool IsInitialDatabase() => string.Equals(m_initialDatabase, Database, StringComparison.Ordinal);
-
-	public int ConnectionId { get; set; }
 }

src/MySqlConnector/Core/ResultSet.cs

@@ -48,6 +48,8 @@ public async Task ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 					if (ok.LastInsertId != 0)
 						Command?.SetLastInsertedId((long) ok.LastInsertId);
 					WarningCount = ok.WarningCount;
+					if (ok.NewSchema is not null)
+						Connection.Session.DatabaseOverride = ok.NewSchema;
 					m_columnDefinitions = default;
 					State = (ok.ServerStatus & ServerStatus.MoreResultsExist) == 0
 						? ResultSetState.NoMoreData

src/MySqlConnector/Core/ServerSession.cs

@@ -44,20 +44,22 @@ public ServerSession(ILogger logger, ConnectionPool? pool, int poolGeneration, i
 		m_activityTags = [];
 		DataReader = new();
 		Log.CreatedNewSession(m_logger, Id);
-		Context = new Context(0, null, 0);
+		Context = new Context(default);
 	}
 
 	public string Id { get; }
 	public ServerVersion ServerVersion { get; set; }
 	public bool SupportsPerQueryVariables => ServerVersion.IsMariaDb && ServerVersion.Version >= ServerVersions.MariaDbSupportsPerQueryVariables;
 	public int ActiveCommandId { get; private set; }
 	public int CancellationTimeout { get; private set; }
+	public int ConnectionId { get; set; }
 	public byte[]? AuthPluginData { get; set; }
 	public long CreatedTimestamp { get; }
 	public ConnectionPool? Pool { get; }
 	public int PoolGeneration { get; }
 	public long LastLeasedTimestamp { get; set; }
 	public long LastReturnedTimestamp { get; private set; }
+	public string? DatabaseOverride { get; set; }
 
 	public string HostName { get; private set; }
 	public IPEndPoint? IPEndPoint => m_tcpClient?.Client.RemoteEndPoint as IPEndPoint;
@@ -338,8 +340,8 @@ public void FinishQuerying()
 		var activity = ActivitySourceHelper.StartActivity(name, m_activityTags);
 		if (activity is { IsAllDataRequested: true })
 		{
-			if (!Context.IsInitialDatabase())
-				activity.SetTag(ActivitySourceHelper.DatabaseNameTagName, Context.Database);
+			if (DatabaseOverride is not null)
+				activity.SetTag(ActivitySourceHelper.DatabaseNameTagName, DatabaseOverride);
 			if (tagName1 is not null)
 				activity.SetTag(tagName1, tagValue1);
 		}
@@ -452,15 +454,16 @@ public async Task DisposeAsync(IOBehavior ioBehavior, CancellationToken cancella
 			}
 
 			ServerVersion = new(initialHandshake.ServerVersion);
-			Context = new Context(initialHandshake.ProtocolCapabilities, cs.Database, initialHandshake.ConnectionId);
+			ConnectionId = initialHandshake.ConnectionId;
+			Context = new Context(initialHandshake.ProtocolCapabilities);
 			AuthPluginData = initialHandshake.AuthPluginData;
 			m_useCompression = cs.UseCompression && (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.Compress) != 0;
 			CancellationTimeout = cs.CancellationTimeout;
 			UserID = cs.UserID;
 
 			// set activity tags
 			{
-				var connectionId = Context.ConnectionId.ToString(CultureInfo.InvariantCulture);
+				var connectionId = ConnectionId.ToString(CultureInfo.InvariantCulture);
 				m_activityTags[ActivitySourceHelper.DatabaseConnectionIdTagName] = connectionId;
 				if (activity is { IsAllDataRequested: true })
 					activity.SetTag(ActivitySourceHelper.DatabaseConnectionIdTagName, connectionId);
@@ -499,7 +502,7 @@ public async Task DisposeAsync(IOBehavior ioBehavior, CancellationToken cancella
 				}
 			}
 
-			Log.SessionMadeConnection(m_logger, Id, ServerVersion.OriginalString, Context.ConnectionId, m_useCompression, m_supportsConnectionAttributes, Context.SupportsDeprecateEof, Context.SupportsCachedPreparedMetadata, serverSupportsSsl, Context.SupportsSessionTrack, m_supportsPipelining, Context.SupportsQueryAttributes);
+			Log.SessionMadeConnection(m_logger, Id, ServerVersion.OriginalString, ConnectionId, m_useCompression, m_supportsConnectionAttributes, Context.SupportsDeprecateEof, Context.SupportsCachedPreparedMetadata, serverSupportsSsl, Context.SupportsSessionTrack, m_supportsPipelining, Context.SupportsQueryAttributes);
 
 			if (cs.SslMode != MySqlSslMode.None && (cs.SslMode != MySqlSslMode.Preferred || serverSupportsSsl))
 			{
@@ -532,18 +535,23 @@ public async Task DisposeAsync(IOBehavior ioBehavior, CancellationToken cancella
 			if (m_useCompression)
 				m_payloadHandler = new CompressedPayloadHandler(m_payloadHandler.ByteHandler);
 
-			// set 'collation_connection' to the server default
-			if (Context.ClientCharset == null || ServerVersion.Version >= ServerVersions.SupportsUtf8Mb4
-				    ? !string.Equals(Context.ClientCharset, "utf8mb4", StringComparison.Ordinal)
-				    : !string.Equals(Context.ClientCharset, "utf8", StringComparison.Ordinal))
+			if (ok.ClientCharacterSet != (ServerVersion.Version >= ServerVersions.SupportsUtf8Mb4 ? "utf8mb4" : "utf8"))
 			{
+				// set 'collation_connection' to the server default
 				await SendAsync(m_setNamesPayload, ioBehavior, cancellationToken).ConfigureAwait(false);
 				payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
 				OkPayload.Verify(payload.Span, Context);
 			}
 
 			if (ShouldGetRealServerDetails(cs))
+			{
 				await GetRealServerDetailsAsync(ioBehavior, CancellationToken.None).ConfigureAwait(false);
+			}
+			else if (ok.ConnectionId is int newConnectionId && newConnectionId != ConnectionId)
+			{
+				Log.ChangingConnectionId(m_logger, Id, ConnectionId, newConnectionId, ServerVersion.OriginalString, ServerVersion.OriginalString);
+				ConnectionId = newConnectionId;
+			}
 
 			m_payloadHandler.ByteHandler.RemainingTimeout = Constants.InfiniteTimeout;
 			return statusInfo;
@@ -570,9 +578,9 @@ public async Task<bool> TryResetConnectionAsync(ConnectionSettings cs, MySqlConn
 			ClearPreparedStatements();
 
 			PayloadData payload;
-			if (Context.IsInitialDatabase() &&
-			    ((!ServerVersion.IsMariaDb && ServerVersion.Version.CompareTo(ServerVersions.SupportsResetConnection) >= 0) ||
-			     (ServerVersion.IsMariaDb && ServerVersion.Version.CompareTo(ServerVersions.MariaDbSupportsResetConnection) >= 0)))
+			if (DatabaseOverride is null &&
+				((!ServerVersion.IsMariaDb && ServerVersion.Version.CompareTo(ServerVersions.SupportsResetConnection) >= 0) ||
+				(ServerVersion.IsMariaDb && ServerVersion.Version.CompareTo(ServerVersions.MariaDbSupportsResetConnection) >= 0)))
 			{
 				if (m_supportsPipelining)
 				{
@@ -599,14 +607,14 @@ public async Task<bool> TryResetConnectionAsync(ConnectionSettings cs, MySqlConn
 			else
 			{
 				// optimistically hash the password with the challenge from the initial handshake (supported by MariaDB; doesn't appear to be supported by MySQL)
-				if (Context.IsInitialDatabase())
+				if (DatabaseOverride is null)
 				{
 					Log.SendingChangeUserRequest(m_logger, Id, ServerVersion.OriginalString);
 				}
 				else
 				{
-					Log.SendingChangeUserRequestDueToChangedDatabase(m_logger, Id, Context.Database!);
-					Context.Database = cs.Database;
+					Log.SendingChangeUserRequestDueToChangedDatabase(m_logger, Id, DatabaseOverride);
+					DatabaseOverride = null;
 				}
 				var password = GetPassword(cs, connection);
 				var hashedPassword = AuthenticationUtility.CreateAuthenticationResponse(AuthPluginData!, password);
@@ -1668,8 +1676,8 @@ static void ReadRow(ReadOnlySpan<byte> span, out int? connectionId, out ServerVe
 
 			if (connectionId is int newConnectionId && serverVersion is not null)
 			{
-				Log.ChangingConnectionId(m_logger, Id, Context.ConnectionId, newConnectionId, ServerVersion.OriginalString, serverVersion.OriginalString);
-				Context.ConnectionId = newConnectionId;
+				Log.ChangingConnectionId(m_logger, Id, ConnectionId, newConnectionId, ServerVersion.OriginalString, serverVersion.OriginalString);
+				ConnectionId = newConnectionId;
 				ServerVersion = serverVersion;
 			}
 		}

src/MySqlConnector/MySqlConnection.cs

@@ -490,7 +490,7 @@ private async Task ChangeDatabaseAsync(IOBehavior ioBehavior, string databaseNam
 		OkPayload.Verify(payload.Span, m_session.Context);
 
 		// for non session tracking servers
-		m_session.Context.Database = databaseName;
+		m_session.DatabaseOverride = databaseName;
 	}
 
 	public new MySqlCommand CreateCommand() => (MySqlCommand) base.CreateCommand();
@@ -628,7 +628,7 @@ public override string ConnectionString
 		}
 	}
 
-	public override string Database => m_session?.Context.Database ?? GetConnectionSettings().Database;
+	public override string Database => m_session?.DatabaseOverride ?? GetConnectionSettings().Database;
 
 	public override ConnectionState State => m_connectionState;
 
@@ -639,7 +639,7 @@ public override string ConnectionString
 	/// <summary>
 	/// The connection ID from MySQL Server.
 	/// </summary>
-	public int ServerThread => Session.Context.ConnectionId;
+	public int ServerThread => Session.ConnectionId;
 
 	/// <summary>
 	/// Gets or sets the delegate used to provide client certificates for connecting to a server.

src/MySqlConnector/Protocol/Payloads/OkPayload.cs

@@ -13,6 +13,9 @@ internal sealed class OkPayload
 	public ServerStatus ServerStatus { get; }
 	public int WarningCount { get; }
 	public string? StatusInfo { get; }
+	public string? NewSchema { get; }
+	public string? ClientCharacterSet { get; }
+	public int? ConnectionId { get; }
 
 	public const byte Signature = 0x00;
 
@@ -57,6 +60,9 @@ public static void Verify(ReadOnlySpan<byte> span, Context context) =>
 		var lastInsertId = reader.ReadLengthEncodedInteger();
 		var serverStatus = (ServerStatus) reader.ReadUInt16();
 		var warningCount = (int) reader.ReadUInt16();
+		string? newSchema = null;
+		string? clientCharacterSet = null;
+		int? connectionId = null;
 		ReadOnlySpan<byte> statusBytes;
 
 		if (context.SupportsSessionTrack)
@@ -75,7 +81,7 @@ public static void Verify(ReadOnlySpan<byte> span, Context context) =>
 						switch (kind)
 						{
 							case SessionTrackKind.Schema:
-								context.Database = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
+								newSchema = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
 								break;
 
 							case SessionTrackKind.SystemVariables:
@@ -90,10 +96,10 @@ public static void Verify(ReadOnlySpan<byte> span, Context context) =>
 									switch (variableSv)
 									{
 										case "character_set_client":
-											context.ClientCharset = valueSv;
+											clientCharacterSet = valueSv;
 											break;
 										case "connection_id":
-											context.ConnectionId = Convert.ToInt32(valueSv, CultureInfo.InvariantCulture);
+											connectionId = Convert.ToInt32(valueSv, CultureInfo.InvariantCulture);
 											break;
 									}
 								} while (reader.Offset < systemVariableOffset);
@@ -126,31 +132,34 @@ public static void Verify(ReadOnlySpan<byte> span, Context context) =>
 		{
 			var statusInfo = statusBytes.Length == 0 ? null : Encoding.UTF8.GetString(statusBytes);
 
-			if (affectedRowCount == 0 && lastInsertId == 0 && warningCount == 0 && statusInfo is null)
+			if (affectedRowCount == 0 && lastInsertId == 0 && warningCount == 0 && statusInfo is null && newSchema is null && clientCharacterSet is null && connectionId is null)
 			{
 				if (serverStatus == ServerStatus.AutoCommit)
 					return s_autoCommitOk;
 				if (serverStatus == (ServerStatus.AutoCommit | ServerStatus.SessionStateChanged))
 					return s_autoCommitSessionStateChangedOk;
 			}
 
-			return new OkPayload(affectedRowCount, lastInsertId, serverStatus, warningCount, statusInfo);
+			return new OkPayload(affectedRowCount, lastInsertId, serverStatus, warningCount, statusInfo, newSchema, clientCharacterSet, connectionId);
 		}
 		else
 		{
 			return null;
 		}
 	}
 
-	private OkPayload(ulong affectedRowCount, ulong lastInsertId, ServerStatus serverStatus, int warningCount, string? statusInfo)
+	private OkPayload(ulong affectedRowCount, ulong lastInsertId, ServerStatus serverStatus, int warningCount, string? statusInfo, string? newSchema, string? clientCharacterSet, int? connectionId)
 	{
 		AffectedRowCount = affectedRowCount;
 		LastInsertId = lastInsertId;
 		ServerStatus = serverStatus;
 		WarningCount = warningCount;
 		StatusInfo = statusInfo;
+		NewSchema = newSchema;
+		ClientCharacterSet = clientCharacterSet;
+		ConnectionId = connectionId;
 	}
 
-	private static readonly OkPayload s_autoCommitOk = new(0, 0, ServerStatus.AutoCommit, 0, null);
-	private static readonly OkPayload s_autoCommitSessionStateChangedOk = new(0, 0, ServerStatus.AutoCommit | ServerStatus.SessionStateChanged, 0, null);
+	private static readonly OkPayload s_autoCommitOk = new(0, 0, ServerStatus.AutoCommit, 0, default, default, default, default);
+	private static readonly OkPayload s_autoCommitSessionStateChangedOk = new(0, 0, ServerStatus.AutoCommit | ServerStatus.SessionStateChanged, 0, default, default, default, default);
 }